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Silent Spring
United States Fish and Wildlife Service Special Wildlife Survey 1996 Abstract During the years 1992-1996, it was observed that the local birds in and around Faulkner Wildlife Refuge in southern Missouri had been unusually quiet. In 1996, the US Fish and Wildlife Service conducted a qualitative wildlife survey of the refuge. The goal of the survey was to determine any probable causes of this phenomenon, and what, if any, steps should be taken in response. Summary In 1992, FWS employees working at Faulkner Wildlife Refuge in Ozark County, Missouri reported that the population of all types of birds at the area seemed to be vocalizing far less often than normal. Throughout the year, they reported hearing far less birdsong than during previous years, including the vocalizations of nocturnal birds such as owls. These reports continued until 1996, when a study was authorized to address this information. The objectives of the wildlife survey were as follows: 1. To determine if birdsong in the area had indeed diminished, or if the employees were mistaken. 2. If there was in fact less birdsong, to determine if the cause was fewer birds in the area or less vocalization per individual specimen. 3. To determine the specific cause of 2, if 1 was found positive. 4. To recommend corrective action, if appropriate. Methodology This wildlife survey was primarily qualitative, but some quantitative methods were included. Stationary microphones and cameras were placed in various points around the Refuge, and field teams were sent out. Sound-file stimulation was also used, particularly for owl species. The first objective was to determine if the local bird populations had decreased. After a few weeks, it was determined that bird populations in and around the Refuge had remained relatively stable compared to past surveys. The next objective was to determine if bird vocalizations had diminished. No wildlife survey focused on vocalizations had been conducted at Faulkner Refuge, so vocalizations at the site were compared with vocalizations at neighboring areas to establish a baseline. Using a combination of microphones and subjective determinations, it was determined that birdsong in the area was indeed abnormally absent. One notable exception to this was an apparent increase in vocalizations from corvids, including crows, ravens, and bluejays. Owl vocalizations were also less frequent, though this may actually have been related to a decrease in the local owl population. Sound-file stimulation, which is usually an easy way to locate owls (especially barred owls and great horned owls, both of which are common in Missouri) produced infrequent responses. Combined use of microphones, cameras, night-visions, and FLIRs revealed the population density of local owl species to be lower than normal at Faulkner Refuge. Several causes for the reduction in birdsong were speculated. Air quality monitors were set up to discover if the cause could be a chemical leak. Results The survey concluded that overall bird vocalizations were less frequent than normal at Faulkner Wildlife Refuge, with the exception of corvids. With the exception of owls, this decrease did not appear to be related to any changes in local bird populations. Several factors were identified as possible causes of this phenomenon. Poachers may have been a contributing factor. During the survey, dozens of illegal tree stands were found on the Refuge, and one poacher was arrested. Another contributing factor may have been increased construction and development near the refuge. While the results of this survey were inconclusive, it was determined that there was no need for immediate action. Conclusion Addendum TOP SECRET